Mr. Obama comes back

There is a price to pay when a president appears disengaged, and President Obama obviously learned how much his diffidence cost him in the first debate this month. On Tuesday night, in the second debate, he regained full command of his vision and his legacy, leaving Mitt Romney sputtering with half-answers, deceptions and one memorable error.

Instead of windy and lethargic answers, the president was crisp in reciting his accomplishments and persuasive in explaining how he has restarted economic growth. Instead of letting Mr. Romney get away with a parade of falsehoods and unworkable promises, he regularly and forcefully called his opponent wrong. Having left many supporters wondering after the first debate whether he really wanted another four years, he finally seemed like a man who was ready to fight for another term.

What he did not do was describe how a second term would be more successful than his first has been, and, in particular, show how he would cut through the thicket of Republican opposition if re-elected. He missed opportunities to call for a more forceful opposition to assault weapons in another term, and to put forward a clear immigration policy.

But the contrast with the weak and failed ideas that Mr. Romney proposed could not have been clearer. The president noted that he had signed legislation that increased pay equity for women; Mr. Romney not only refused to say whether he would have done so, but condescendingly said he had hired many women when he was the governor of Massachusetts and had given them flexible schedules.

Mr. Obama pointed out that Mr. Romney’s tax numbers did not add up, and called the plan a “sketchy deal”; Mr. Romney responded in a huff. “Of course they add up,” he said. “I was someone who ran businesses for 25 years and balanced the budget.” Apparently he thinks it should be self-evident that a private equity mogul knows how to cut taxes drastically and still balance the budget, but it is not evident to any of the independent experts who have looked at his plan, as Mr. Obama icily pointed out.

The president reminded listeners that Mr. Romney’s immigration adviser was the author of Arizona’s radical, unconstitutional immigration law. And Mr. Romney himself repeated his cruel prescription to have undocumented immigrants “self-deport” by making it impossible for them to find work and aggressively demanding their identification papers. Mr. Obama offered the better, broader view on fixing immigration, though his own administration has also deported tens of thousands of noncriminals through a crackdown similar to Arizona’s law.

The president even got off a few good lines, pointing out that his pension was considerably smaller than Mr. Romney’s, and that his opponent was far more extreme than President George W. Bush in proposing to turn Medicare into a voucher system and to eliminate financing for Planned Parenthood. He finally took the opportunity to bring up Mr. Romney’s dismissal of 47 percent of the country as people who consider themselves victims and do not take personal responsibility for their lives.

But the most devastating moment for Mr. Romney was self-inflicted. Continuing his irresponsible campaign to politicize the death of the American ambassador to Libya, he said it took two weeks for the president to acknowledge that it was the result of an act of terror. As the moderator, Candy Crowley of CNN, quickly pointed out, the president referred to it as an act of terror the next day, in the Rose Garden. “Can you say that a little louder, Candy?” asked Mr. Obama, having fully regained his stride and confidence.

Voters who watched the first debate might have been left with an impression that Mr. Romney was the candidate of ideas and that Mr. Obama’s reserves of energy and seriousness had been tapped out. On Tuesday night, those roles were reversed.